In certain parts of the world, such as France and Brazil, the "heart" or center portion of the stalk of the palmetto palm tree is considered a great delicacy for human consumption. Until now, it has, for the most part, been harvested in the wild, primarily in Brazil, where it is packed fresh in tins for domestic consumption and for export.
The palmetto palm comprises a "meristem" portion, which is the lowest (approximately) 1.5 meters (4.9.+-. ft.) of the exposed portion of the growing plant, and, above that, a main stalk portion, of which about 2/3+ meter (2.4+ ft.) is useful as a source for palmheart extraction. The meristem portion of the stalk is normally significantly larger in diameter (i.e., it is about 7.6 cm. or 3 inches) than is the upper portion of the exposed stalk, which is about 5.1 cm. or 2 inches in diameter. The two sections are connected by a tapered section of stalk which, in cross section, is roughly in the shape of an inverted, truncated cone. The processing steps for recovering palmheart sections traditionally have included field cutting an approximately 1 meter length of stalk from that portion of growing plant which includes a portion of the upper, main stalk that is about 2/3 meter (2.4 ft.) in length, and about 1/3 meter (1.2 ft.) of the upper part of the meristem portion, and the interposed tapered section, all as one piece. The object in such harvesting and the subsequent processing which takes place is to recover the very inside, or "heart" of the stalk from the entire harvested length. That traditionally has been done manually, using a knife to slit longitudinally the bark and the intermediate layer of the upper stalk portion, and by coring the meristem portion.
The narrower portion of the cut length of stalk is more or less round in cross section and has an outer bark layer which, while not as hard as some tree bark, is nevertheless very firm and tough. Therefore, the existing practice, as a prerequisite to removing the bark layer, is to steam the field-cut stalks in an autoclave for about 1/2 hour at about 125 degrees C. to soften the outermost or bark layer. More significantly, however, as harvested, the stalks are covered on the outside with fairly long, very sharp thorn-like projections. Even though they tend to lie at a shallow angle to the surface of the stalk rather than at right angles to it, these projections make the stalks difficult to handle and process. The outer bark layer encloses an intermediate layer which is also more or less circular in cross section, tough (but less tough than the bark layer), and, in the upper portion of a stalk whose outer diameter of the bark layer is about 5.1 cm. (2 inches), is about 3.5 cm. (1 3/8 inches) in diameter. The intermediate layer typically is somewhat larger in the meristem portion, while the innermost or palmheart section is substantially of uniform diameter throughout the upper, tapered and meristem sections. The palmheart itself, which lies within the intermediate layer, is more or less circular in cross section and, in the example given, is about 1.9 cm. (3/4 inch) in diameter. However, the periphery of the intermediate layer is eccentric with respect to the periphery of the outer bark layer. Further, the palmheart itself is eccentric but with respect to the periphery of the intermediate layer and usually with respect to the outer bark layer also. These circumstances are of less moment as to the meristem and tapered portions because coring type techniques may be used to remove the palmheart from those portions. However, these eccentricities, which (in cross section taken through the stalk) normally are not correspondingly positioned, complicate greatly the harvesting of the heart, particularly from the smaller diameter top section.
Traditionally, removal of the palmheart portions from these upper portions is done by people who use very sharp knives to split lengthwise first the outer bark layer of the stalk which is then torn away from that which underlies it, and then the intermediate layer which is then torn away from the underlying palmheart. The depth of any cut made in either of these layers to remove it from that which is underneath must be made with particular attention so as not to cut through it into the the underlying palmheart portion as well. Further, since the orientation of the eccentricities of the two outer layers is not the same, it is necessary usually to remove the outer and intermediate layers in separate, sequential steps, between which the stalks are reoriented by turning them. By this means, it is assured that the cuts are made through the thickest parts of each such layer, to minimize the possibility of cut-through. This is further complicated by the pronounced increase in the cross sectional "diameter" of the stalk moving past the tapered portion to the meristem portion from the upper or main portion of the stalk. (In the context of his disclosure it is to be understood that rarely is any portion of a stalk truly circular in cross section, but rather usually it is merely irregularly round, and thus by its "diameter" is meant the average of several mean distances taken across its cross-section). Since there is an annular ring in the region of the tapered portion which is comparatively weak that forms the juncture between the tapered portion and the upper portion of the stalk, usually bending the outer bark layer away from the upper part of the stalk which it surrounds causes it to snap at the juncture and separate from the the remainder of the stalk. Thereafter, the upper portion, now consisting of the intermediate layer-covered palmheart portion is severed from the remainder of the stalk and the palmheart is removed from it by linearly slitting its intermediate layer and stripping that layer away from the underlying palmheart core. It is to the phases of such removal of the outer bark form the upper portion of the stalk, severing that upper portion from the remainder of the stalk, and removal of the intermediate layer of that upper portion from the palmheart which it surrounds that this invention is directed.
Concurrently with and/or sequentially and independently from those operations, the palmheart may be removed from the remainder of the original stalk, which now consists of the bark covered meristem portion and the adjacent bark covered tapered portion, by coring it out, manually, or by using mechanical means such as a tubular knife that is thrust axially to separate and extract the palmheart portion from it.
Obviously, all of this is very labor intensive, and since the recovered palmheart cannot be preserved for an appreciably length of time, must be done at or very near the place of harvesting. For these reasons, the price for this commodity traditionally has been very high. Recently, there have been efforts to raise palmettos for palmheart harvesting on plantations, to make the growing and harvesting of them easier and less expensive and to facilitate the rapid transport of cut stalks to processing locations. This also produces products of higher quality and better uniformity than can be obtained with cuttings from growth in the wild. The less wide range in "diameter" of plantation stalks, whose ages are more easily unified than is possible with wild stock, has led to interest in automating selected phases of the process, since this also can have the additional advantages of improving the quality of the product and making processing less expensive.
Accordingly, it is an object of this invention to provide means to recover palmhearts from palm stalks.
Another object of this invention is to provide such means which is mechanized.
Still another object of this invention is to provide means for satisfying one or more of the foregoing objectives which is adapted to accommodate substantial diameter variations between and within individual palm stalks as they are being processed.
Yet another object of this invention is to provide means for satisfying one or more of the foregoing objectives which is adapted to remove the intermediate and outer layers from the associated palmheart while preserving the associated meristem portion for further processing.